DETECTION OF INHIBITORY SUBSTANCES IN MILK

Transcription

1 DETECTION OF INHIBITORY SUBSTANCES IN MILK DELVOTEST P 5 PACK/Visual & DelvoScan Reader (raw commingled cow milk, raw commingled goat milk and NCIMS accepted pasteurized cow and goat milk products) [Unless otherwise stated all tolerances are ±5%] GENERAL REQUIREMENTS 1. Laboratory Requirements (see Cultural Procedures (CP) items 34 & 35), except a. For Appendix N testing, see Appendix N General Requirements (App. N GR) items 14 & 15 SAMPLES 2. See CP item 33, except a. For Appendix N testing, see App. N GR item 9 APPARATUS & REAGENTS 3. See CP items 1-23, except a. For Appendix N testing, see App. N GR items Equipment a. Dry incubator and/or water bath thermostatically controlled at 64±2 C b. Heating block, water bath or other acceptable method to heat to at least 82±2 C, for confirmation c. Pipettor - 100µL and disposable tips (see App. N GR Item 7 or CP item 6) d. Forceps, Tablet Dispenser, or equivalent e. Test tubes for beta-lactam confirmation f. Timer g. DelvoScan Reader (optional) (approved for white milk only) 1. Software version: 2. Scanner: ( ) FORM FDA 2400b-3 Delvotest P 5 Pack Rev Page 1 of 8

2 a. Instrument calibrated once every 30 days b. Latest calibration date: 3. Computer with Windows operating system 4. Printer: 5. Kodak Q-60 5x7 color reference photo card 6. Black/Dark cloth for scanner background 5. Reagents a. Delvotest P 5 Pack Kit 1. Kit: Lot #: Exp. Date: QC Date: By: 2. Store kits at 0-15 C 3. Bottle of nutrient tablets Lot #: a. Once opened for use, maintain nutrient tablets in original bottle at room temperature with desiccant b. Discard remaining nutrient tablets when last wells are used. Do not mix with other kits b. Commercial Standard (milk based), 5.0 ppb Penicillin G Positive Control Mfr: Lot #: Exp. Date: 1. Store according to label instructions 2. Rehydrate according to manufacturer's instructions 3. Store rehydrated solution according to manufacturer s instructions Lab Prep. Date: Lab Exp. Date: 4. Or, aliquot within 24 hours and freeze at 15 C or colder in non frost-free freezer or in an insulated foam container in a frost-free freezer; use within 2 months. (Once thawed, maintain control according to manufacturer s instructions and use within 24 hours) Lab Prep. Date: Lab Exp. Date: FORM FDA 2400b-3 Delvotest P 5 Pack Rev Page 2 of 8

3 c. Negative Control 1. Inhibitor Free Raw Milk a. Sample ID: Date Tested: b. Store solution at C for no more than 72 hrs c. Or, aliquot within 24 hours and freeze at 15 C or colder in non frost-free freezer or in an insulated foam container in a frost-free freezer; use within 2 months. (Once thawed, store control at C and use within 24 hours) Lab Prep. Date: Lab Exp. Date: 2. Commercially Available Negative Control Mfr: Lot #: Exp Date: a. Store according to label instructions b. Rehydrate according to manufacturer's instructions c. Store rehydrated solution according to manufacturer s instructions d. Or, aliquot within 24 hours and freeze at 15 C or colder in non frost-free freezer or in an insulated foam container in a frost-free freezer; use within 2 months (Once thawed, maintain according to manufacturer s instructions) Lab Prep. Date: Lab Exp. Date: d. Beta-lactamase (not required if beta-lactamase is not used for confirmation) Mfr: Lot #: Exp. Date: 1. Store according to manufacturer's instructions 2. Do not use beyond expiration date TECHNIQUE 6. Performance Check (see App N GR item 10.a) a. Positive and negative controls give appropriate color reactions prior to any sample analysis (refers to new lot numbers) b. Take corrective action for inappropriate color reaction(s) FORM FDA 2400b-3 Delvotest P 5 Pack Rev Page 3 of 8

4 c. Maintain records 7. Test Procedure a. Depending on the number of samples to be tested, take out a sufficient number of whole multi-plates and/or cut off the number of wells needed b. Identify samples/controls c. Use one positive and one negative control with each set of samples tested, 94 samples (item 5) d. Remove aluminum top foil e. Using forceps or tablet dispenser (or equivalent), add one nutrient tablet to each test well f. Sample agitation 1. Mix raw milk sample(s)/control(s) (approx ¾ full), subsample(s) of retail milk containers or control(s) by shaking 25 times in 7 sec with a 1 ft movement or vortex for 10 sec at maximum setting; use within 3 min (samples/controls must be in appropriate container to allow the use of vortexing) 2. Mix retail milk samples by inverting containers top to bottom then bottom to top (a complete half circle or 180 degrees) without pausing, 25 times; use within 3 min g. Add 100 µl of mixed sample/control to appropriate test well 1. Using pipettor (item 4.c) with new tip for each sample/control, draw up 100 µl avoiding foam and bubbles 2. Remove tip from liquid 3. Expel test portion into appropriate test well a. If pipettor has two (2) stops, depress plunger to second stop h. Seal wells with adhesive strips provided with test kits i. Incubate at 64±2 C for the time period specified by the manufacturer. Time is approximate and test is complete when controls give proper color reactions j. Remove from dry incubator or water bath and visually read test result from the bottom FORM FDA 2400b-3 Delvotest P 5 Pack Rev Page 4 of 8

5 8. Results a. Visual reading of multi-plates 1. A yellow or yellow/purple color of the agar indicates the absence of inhibitory substances. Result is negative 2. A purple color of the agar indicates the presence of inhibitory substances. Result is an initial or presumptive positive. Confirm as in item 9 below b. Optionally read multi-plates with DelvoScan Reader (Multi-plates from water bath must be dried off prior to further handling) 1. Start DelvoScan software by double click on icon a. Select test (Delvo P 5 Pack) and press next b. Input operator, sample and test kit data 1. Enter number of test on scan-bed 2. Enter test kit lot number 3. Enter sample data c. Press SCAN and results will be displayed d. Press PRINT to obtain hard copy result data e. Samples that read DelvoScan negative (<NEG>), inhibitor not detected f. Samples that read DelvoScan positive (<POS>), must be confirmed (see item 9) c. Maintain records 9. Confirmation of PMO Section 6 Samples or Verification of Appendix N Initial Positive Tanker Samples (see App. N GR item 11); Confirmation of Presumptive Positive Tanker Samples (see App. N GR item 12); and if applicable, Traceback of Producer(s) on a Confirmed Positive Tanker (see App. N GR item 13). PROMPTLY retest the SAME sample in DUPLICATE along with a positive and negative control as described below (9.a.1-12) a. Inhibitor confirmation/verification and optional beta-lactamase confirmation FORM FDA 2400b-3 Delvotest P 5 Pack Rev Page 5 of 8

6 1. Confirmation (without beta-lactamase) a. Prepare a tube of each suspect sample b. Prepare a tube of positive control milk (item 5.b) c. Prepare a tube of negative control (item 5.c) d. Heat all tubes to 82±2 C for 2 min (TC required) e. Remove and cool rapidly in an ice bath to room temperature or below 2. Confirmation using beta-lactamase (optional by State Regulatory Agency) a. Prepare two tubes of each suspect sample and two tubes for the positive and negative controls b. Heat all tubes to 82±2 C for 2 min (TC required) c. Remove and cool rapidly in an ice bath to room temperature or below d. Add beta-lactamase to one tube of each sample and control 3. Cut off enough wells for all sample and control tubes a. Or, alternatively Delvotest P/SP Mini ampoules may be used for raw samples (analyst(s) must be certified for this procedure) 4. Remove top foil and add one (1) nutrient tablet to each test well 5. Mix tubes, as in 7.f.1, and add 100 µl of mixed sample/control to corresponding test well as in 7.g 6. Change pipettor tips for each sample/control 7. Seal wells with adhesive strips provided with test kit 8. Place sealed blocks in pre-warmed dry incubator or water bath and incubate at 64±2 C for the time period specified by the manufacturer. Time is approximate and test is complete when controls give proper color reactions 9. Remove from dry incubator or water bath and visually read test result from the bottom side FORM FDA 2400b-3 Delvotest P 5 Pack Rev Page 6 of 8

7 10. Optionally read multi-plates with DelvoScan Reader (Multi-plates from water bath must be dried off prior to further handling). See item 8.b for instructions 11. Record the color reactions (item 8.a) of all samples and controls 12. Controls give appropriate reactions/colors, if not repeat testing of all samples and controls a. If control(s) fail again, contact State regulatory and send sample, along with temperature control to an accredited laboratory for confirmation (must comply with M-a-85 (latest revision) and App. N of the PMO) b. Seek technical assistance b. Results of Presumptive Positive and Confirmation Tests 1. Yellow or yellow/purple color of the agar in both duplicates OR, DelvoScan negative (<NEG>), indicates the absence of inhibitory substances. Result is negative 2. Purple color of the agar OR a DelvoScan positive (<POS>), indicates the presence of inhibitory substances. Result is confirmed positive 3. Maintain records c. Results of optional beta-lactamase test: 1. If the agar of the untreated milk sample is yellow or yellow/purple, or DelvoScan negative (<NEG>) and the corresponding agar of the beta-lactamase treated milk sample is yellow or yellow/purple, or DelvoScan negative (<NEG>), inhibitor not detected 2. If the agar of the untreated milk sample is purple or DelvoScan positive (<POS>) and the corresponding agar of the beta-lactamase treated milk sample is yellow or yellow/purple, or DelvoScan negative (<NEG>), sample is positive for beta-lactam, 3. If the agar of the untreated milk sample is purple or DelvoScan Positive (<POS>) and the corresponding agar of the beta-lactamase treated milk sample is also purple or DelvoScan positive (<POS>), sample is positive for inhibitor (non-beta-lactam) 4. If the agar of the untreated milk sample is yellow or yellow/purple or DelvoScan negative (<NEG>) and the corresponding agar of the beta-lactamase treated milk sample is purple or DelvoScan positive (<POS>), test is invalid, repeat test FORM FDA 2400b-3 Delvotest P 5 Pack Rev Page 7 of 8

8 5. Maintain records d. Confirmation of Appendix N samples, see App. N GR form items 12-13, perform confirmation as in items 9.a.1-12 above (use of beta-lactamase required) and interpret as in item 9.b-c above e. Verification of Initial Positive Tanker (see App. N GR item 11). Samples using beta-lactam specific test kit; conduct test as in respective FORM FDA 2400 for the test kit; if beta-lactam not detected in either sample duplicate, verify sample using the Delvotest P test kit as described in item 9.a.1-12 above 10. Recording and Reporting (for Appendix N also see App. N GR item 14) a. Record results of samples and controls performed b. Report presence of inhibitor only for heated milk samples c. If inhibitor is not detected report as Not Found (NF) d. Report presence of inhibitor as Positive (+) or Positive for beta-lactam (if confirmed with beta-lactamase as in item 9.a.2 & 9.c); report to State Regulatory Agency e. If inhibitor is present, bacteria counts cannot be reported FORM FDA 2400b-3 Delvotest P 5 Pack Rev Page 8 of 8